Application of Tethered Ruthenium Catalysts to Asymmetric Hydrogenation of Ketones, and the Selective Hydrogenation of Aldehydes

Abstract

, 1974-and Wills, Martin. (2012 Application of tethered ruthenium catalysts to asymmetric hydrogenation of ketones, and the selective Hydrogenation of aldehydes. Advanced Synthesis & Catalysis, 354 (13). pp. 2545-2555. Permanent WRAP url:http://wrap.warwick.ac.uk/55017 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available. Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Abstract. An improved method for the synthesis of tethered ruthenium(II) complexes of monosulfonylated diamines is described, together with their application to hydrogenation of ketones and aldehydes. The complexes were applied directly, in their chloride form, to asymmetric ketone hydrogenation, to give products in excess of 99% ee in the best cases, using 30 bar of hydrogen at 60 °C , and to the selective reduction of aldehydes over other functional groups.

Direct Formation of Tethered Ru(II) Catalysts Using Arene Exchange

“…Improved synthetic approaches to 2 ( n = 1) 7,8a require conversion of the alcohol from step (i) to the tosylate, triflate, or mesylate and coupling with the diamine component, and also combine the last two stages into one. In alternative approaches, a [4 + 2] cycloaddition may be employed to form the required diene.…”

Development of a Stepwise Reductive Deoxygenation Process by Ru‐Catalysed Homogeneous Ketone Reduction and Pd‐Catalysed Hydrogenolysis in the Presence of Cu Salts

“…These results confirmed the advantage of the tethered catalyst design already reported in the area of chiral catalysis. [8,9] The improved results are probably a consequence of increased catalyst robustness in the presence of poly-functionalised substrates.…”

“…[9] Initial tests indicated that different reducing agents were effective: formic acid/triethylamine (5:2 and 1:1 mixtures) as well as sodium formate and ammonium formate in a biphasic system of EtOAc/water. The biphasic system was found to be particularly convenient to facilitate workup and product isolation and rapidly allowed the reduction of the catalyst loading from S/C (equivalents S = substrate/C = catalyst) 1000:1 (Table 1, entry 1) to S/C 5000:1 (entry 2) and S/C 10 000:1 (entry 3).…”

“…[24] Homogeneous catalysts [9,[11][12][13][14][15] and 1 [1,2] were prepared according to literature procedures. HPLC analysis: Waters XBridge C18 column, 4.6 150 mm, 3.5 mm particle size; flow rate = 1.…”

Hydrogen

“…50 In a relatively recent development, tethered ruthenium catalysts (such as those in eq 22) have proven highly effective for the asymmetric reduction of ketones and for selective reduction of aldehydes. 51 Iron catalyzed hydrogenation of ketones is currently under development in an effort to move away from the platinum group metals (due to their cost, low abundance, and toxicity). 52,53 Mechanistically, this takes place through coordination of the ketone to a dearomatized iron center, insertion into the created Fe-H bond, followed by readdition of hydrogen to regenerate the active catalyst.…”